Using remote sensing to monitor Aerosol Optical Thickness (AOT) and its relationship with land cover in Lagos Metropolis, Nigeria

Abstract

Aerosol Optical Thickness (AOT) is the most fundamental parameter for determining the optical properties of aerosols, which can be extracted from remotely sensed images using the atmospheric correction equation for atmospheric reflectance and radiative transfer model. This study used multi-temporal and multi-spectral Landsat imageries of Lagos Metropolis at two epochs (2002 and 2020) to evaluate the AOT levels in the metropolis. The 6S model was used to generate a Look-Up Table (LUT) using Py6S, a python based 6S module. This was used to simulate the AOT using land surface reflectance and top of atmosphere reflectance. A comparative assessment of the method against the ground-based measurements of particulate matter (PM) at three different locations shows a strong positive correlation between the imagery-derived AOT values and PM . Generally, the AOT values increased from 2002 to 2020 and this could be explained by the increased urban expansion in the metropolis. This alarming scenario requires urgent intervention and mitigation efforts. Remote sensing-based AOT monitoring is a possible solution.